"""
State space implementation for the Claude Code POMDP.

This module implements the state space S as defined in the theoretical framework,
including efficient state representation, comparison, and transition operations.
"""

using LinearAlgebra
using Random
using Distributions
using DataStructures

# ============================================================================
# State Space Definition and Operations
# ============================================================================

"""
    ClaudeCodeStateSpace

Represents the complete state space for the Claude Code system.
Implements efficient storage and operations for high-dimensional states.
"""
struct ClaudeCodeStateSpace
    filesystem_patterns::Dict{String, Regex}  # common file patterns
    dependency_templates::Dict{String, Set{String}}  # language-specific deps
    process_signatures::Dict{String, Vector{String}}  # process fingerprints
    tool_configurations::Dict{String, Dict{String, Any}}
    max_states::Int  # maximum number of states to track explicitly
    
    function ClaudeCodeStateSpace(max_states::Int = 10000)
        new(
            Dict{String, Regex}(),
            Dict{String, Set{String}}(),
            Dict{String, Vector{String}}(),
            Dict{String, Dict{String, Any}}(),
            max_states
        )
    end
end

"""
    create_initial_state(workspace_path::String) -> EnvironmentalState

Create the initial environmental state from a workspace directory.
"""
function create_initial_state(workspace_path::String)
    # Scan file system
    filesystem = scan_filesystem(workspace_path)
    
    # Build dependency graph
    dependencies = build_dependency_graph(filesystem)
    
    # Get current process state
    processes = get_current_process_state()
    
    # Detect available tools
    tools = detect_available_tools()
    
    # Get external environment
    external = sample_external_environment()
    
    return EnvironmentalState(filesystem, dependencies, processes, tools, external)
end

"""
    scan_filesystem(path::String) -> FileSystemState

Scan filesystem and create state representation.
"""
function scan_filesystem(path::String)
    files = Dict{String, String}()
    directories = Set{String}()
    permissions = Dict{String, UInt8}()
    modification_times = Dict{String, Float64}()
    
    if !isdir(path)
        @warn "Path $path is not a directory"
        return FileSystemState(files, directories, permissions, modification_times)
    end
    
    # Walk directory tree
    for (root, dirs, filenames) in walkdir(path)
        # Add directories
        push!(directories, root)
        for dir in dirs
            push!(directories, joinpath(root, dir))
        end
        
        # Add files
        for filename in filenames
            filepath = joinpath(root, filename)
            try
                # Read file content (limit to avoid memory issues)
                content = ""
                if isfile(filepath) && filesize(filepath) < 1_000_000  # 1MB limit
                    content = read(filepath, String)
                else
                    content = "[BINARY_OR_LARGE_FILE]"
                end
                
                files[filepath] = content
                
                # Get permissions and modification time
                stat_info = stat(filepath)
                permissions[filepath] = stat_info.mode % UInt8
                modification_times[filepath] = stat_info.mtime
                
            catch e
                @warn "Could not read file $filepath: $e"
                files[filepath] = "[READ_ERROR]"
                permissions[filepath] = 0o000
                modification_times[filepath] = 0.0
            end
        end
    end
    
    return FileSystemState(files, directories, permissions, modification_times)
end

"""
    build_dependency_graph(filesystem::FileSystemState) -> DependencyGraph

Build dependency graph from filesystem analysis.
"""
function build_dependency_graph(filesystem::FileSystemState)
    nodes = Set{String}()
    edges = Set{Tuple{String, String}}()
    weights = Dict{Tuple{String, String}, Float64}()
    node_attributes = Dict{String, Dict{String, Any}}()
    
    # Extract nodes (functions, classes, modules) from files
    for (filepath, content) in filesystem.files
        if content == "[BINARY_OR_LARGE_FILE]" || content == "[READ_ERROR]"
            continue
        end
        
        # Analyze based on file extension
        ext = lowercase(splitext(filepath)[2])
        
        if ext in [".py", ".jl", ".js", ".ts", ".java", ".cpp", ".c", ".h"]
            extracted_nodes, extracted_edges = analyze_code_file(filepath, content, ext)
            
            union!(nodes, extracted_nodes)
            union!(edges, extracted_edges)
            
            # Set default weights
            for edge in extracted_edges
                if !haskey(weights, edge)
                    weights[edge] = 1.0
                end
            end
            
            # Add node attributes
            for node in extracted_nodes
                if !haskey(node_attributes, node)
                    node_attributes[node] = Dict{String, Any}(
                        "file" => filepath,
                        "type" => infer_node_type(node, content),
                        "complexity" => estimate_complexity(node, content)
                    )
                end
            end
        end
    end
    
    return DependencyGraph(nodes, edges, weights, node_attributes)
end

"""
    analyze_code_file(filepath::String, content::String, extension::String)

Analyze code file to extract nodes and dependencies.
Returns (nodes, edges) where nodes are code entities and edges are dependencies.
"""
function analyze_code_file(filepath::String, content::String, extension::String)
    nodes = Set{String}()
    edges = Set{Tuple{String, String}}()
    
    lines = split(content, '\n')
    
    if extension == ".py"
        # Python analysis
        current_class = nothing
        
        for line in lines
            stripped = strip(line)
            
            # Function definitions
            if startswith(stripped, "def ")
                func_match = match(r"def\s+(\w+)", stripped)
                if func_match !== nothing
                    func_name = func_match.captures[1]
                    full_name = current_class !== nothing ? "$current_class.$func_name" : func_name
                    push!(nodes, full_name)
                end
            end
            
            # Class definitions
            if startswith(stripped, "class ")
                class_match = match(r"class\s+(\w+)", stripped)
                if class_match !== nothing
                    current_class = class_match.captures[1]
                    push!(nodes, current_class)
                end
            end
            
            # Import statements
            if startswith(stripped, "import ") || startswith(stripped, "from ")
                import_match = match(r"(?:from\s+(\w+)\s+)?import\s+([^\s#]+)", stripped)
                if import_match !== nothing
                    imported = import_match.captures[2]
                    if imported !== nothing
                        # Add edge from current file to imported module
                        push!(edges, (basename(filepath), strip(imported)))
                    end
                end
            end
        end
        
    elseif extension == ".jl"
        # Julia analysis
        for line in lines
            stripped = strip(line)
            
            # Function definitions
            if startswith(stripped, "function ") || contains(stripped, r"^\w+\(.*\)\s*=")
                func_match = match(r"(?:function\s+)?(\w+)", stripped)
                if func_match !== nothing
                    push!(nodes, func_match.captures[1])
                end
            end
            
            # Struct definitions
            if startswith(stripped, "struct ") || startswith(stripped, "mutable struct ")
                struct_match = match(r"(?:mutable\s+)?struct\s+(\w+)", stripped)
                if struct_match !== nothing
                    push!(nodes, struct_match.captures[1])
                end
            end
            
            # Using statements
            if startswith(stripped, "using ")
                using_match = match(r"using\s+([^\s#,]+)", stripped)
                if using_match !== nothing
                    push!(edges, (basename(filepath), using_match.captures[1]))
                end
            end
        end
    end
    
    return nodes, edges
end

"""
    infer_node_type(node::String, content::String) -> String

Infer the type of a code node (function, class, etc.).
"""
function infer_node_type(node::String, content::String)
    # Simple heuristics based on naming and context
    if occursin("class $node", content)
        return "class"
    elseif occursin("def $node", content) || occursin("function $node", content)
        return "function"
    elseif occursin("struct $node", content)
        return "struct"
    else
        return "unknown"
    end
end

"""
    estimate_complexity(node::String, content::String) -> Float64

Estimate the complexity of a code node.
"""
function estimate_complexity(node::String, content::String)
    # Simple cyclomatic complexity estimation
    complexity_keywords = ["if", "elif", "else", "for", "while", "try", "except", "catch", "&&", "||"]
    
    lines = split(content, '\n')
    complexity = 1.0  # base complexity
    
    for line in lines
        if occursin(node, line)
            for keyword in complexity_keywords
                complexity += count(keyword, lowercase(line))
            end
        end
    end
    
    return min(complexity, 20.0)  # cap at reasonable maximum
end

"""
    get_current_process_state() -> ProcessState

Get the current state of system processes.
"""
function get_current_process_state()
    running_processes = Dict{Int, String}()
    environment_variables = Dict{String, String}()
    system_resources = Dict{String, Float64}()
    
    try
        # Get environment variables
        for (key, value) in ENV
            environment_variables[key] = value
        end
        
        # Get basic system resources
        system_resources["memory_usage"] = 0.0  # Placeholder
        system_resources["cpu_usage"] = 0.0     # Placeholder
        system_resources["disk_usage"] = 0.0    # Placeholder
        
        # On Unix systems, we could use ps command
        if Sys.isunix()
            try
                ps_output = read(`ps -eo pid,comm`, String)
                for line in split(ps_output, '\n')[2:end]  # Skip header
                    parts = split(strip(line), limit=2)
                    if length(parts) >= 2
                        pid = tryparse(Int, parts[1])
                        if pid !== nothing
                            running_processes[pid] = parts[2]
                        end
                    end
                end
            catch e
                @debug "Could not get process list: $e"
            end
        end
        
    catch e
        @debug "Error getting process state: $e"
    end
    
    return ProcessState(running_processes, environment_variables, system_resources)
end

"""
    detect_available_tools() -> ToolConfiguration

Detect available tools in the system.
"""
function detect_available_tools()
    available_tools = Set{String}()
    tool_configurations = Dict{String, Dict{String, Any}}()
    tool_versions = Dict{String, String}()
    disabled_tools = Set{String}()
    
    # Common development tools to check
    tools_to_check = [
        ("git", `git --version`),
        ("python", `python --version`),
        ("julia", `julia --version`),
        ("node", `node --version`),
        ("npm", `npm --version`),
        ("pip", `pip --version`),
        ("cargo", `cargo --version`),
        ("rustc", `rustc --version`),
        ("javac", `javac -version`),
        ("gcc", `gcc --version`),
        ("make", `make --version`)
    ]
    
    for (tool_name, version_cmd) in tools_to_check
        try
            version_output = read(version_cmd, String)
            push!(available_tools, tool_name)
            tool_versions[tool_name] = strip(version_output)
            tool_configurations[tool_name] = Dict{String, Any}(
                "available" => true,
                "version" => strip(version_output),
                "detected_at" => time()
            )
        catch e
            tool_configurations[tool_name] = Dict{String, Any}(
                "available" => false,
                "error" => string(e),
                "detected_at" => time()
            )
        end
    end
    
    return ToolConfiguration(available_tools, tool_configurations, tool_versions, disabled_tools)
end

"""
    sample_external_environment() -> ExternalEnvironment

Sample the current external environment state.
"""
function sample_external_environment()
    network_connectivity = test_network_connectivity()
    system_load = get_system_load()
    available_memory = get_available_memory()
    available_disk = get_available_disk()
    timestamp = time()
    
    return ExternalEnvironment(network_connectivity, system_load, available_memory, available_disk, timestamp)
end

"""
    test_network_connectivity() -> Bool

Test basic network connectivity.
"""
function test_network_connectivity()
    try
        # Simple connectivity test
        run(`ping -c 1 -W 1 8.8.8.8`)
        return true
    catch
        return false
    end
end

"""
    get_system_load() -> Float64

Get current system load average.
"""
function get_system_load()
    try
        if Sys.isunix()
            loadavg = read(`cat /proc/loadavg`, String)
            return parse(Float64, split(loadavg)[1])
        end
    catch
    end
    return 0.0
end

"""
    get_available_memory() -> Float64

Get available memory in bytes.
"""
function get_available_memory()
    try
        if Sys.isunix()
            meminfo = read(`cat /proc/meminfo`, String)
            for line in split(meminfo, '\n')
                if startswith(line, "MemAvailable:")
                    return parse(Float64, match(r"(\d+)", line).captures[1]) * 1024
                end
            end
        end
    catch
    end
    return 0.0
end

"""
    get_available_disk() -> Float64

Get available disk space in bytes.
"""
function get_available_disk()
    try
        if Sys.isunix()
            df_output = read(`df -B1 .`, String)
            lines = split(df_output, '\n')
            if length(lines) >= 2
                fields = split(lines[2])
                if length(fields) >= 4
                    return parse(Float64, fields[4])
                end
            end
        end
    catch
    end
    return 0.0
end

"""
    state_distance(s1::EnvironmentalState, s2::EnvironmentalState) -> Float64

Compute distance between two environmental states.
"""
function state_distance(s1::EnvironmentalState, s2::EnvironmentalState)
    # Weighted combination of component distances
    weights = [0.4, 0.3, 0.1, 0.1, 0.1]  # [filesystem, deps, processes, tools, external]
    
    fs_dist = filesystem_distance(s1.filesystem, s2.filesystem)
    dep_dist = dependency_distance(s1.dependencies, s2.dependencies)
    proc_dist = process_distance(s1.processes, s2.processes)
    tool_dist = tool_distance(s1.tools, s2.tools)
    ext_dist = external_distance(s1.external, s2.external)
    
    return weights[1] * fs_dist + weights[2] * dep_dist + weights[3] * proc_dist + 
           weights[4] * tool_dist + weights[5] * ext_dist
end

"""
    filesystem_distance(fs1::FileSystemState, fs2::FileSystemState) -> Float64

Compute distance between filesystem states.
"""
function filesystem_distance(fs1::FileSystemState, fs2::FileSystemState)
    # Jaccard distance on file sets + content differences
    files1 = Set(keys(fs1.files))
    files2 = Set(keys(fs2.files))
    
    if isempty(files1) && isempty(files2)
        return 0.0
    end
    
    jaccard_sim = length(files1 ∩ files2) / length(files1 ∪ files2)
    
    # Content differences for common files
    content_diff = 0.0
    common_files = files1 ∩ files2
    
    if !isempty(common_files)
        for file in common_files
            if fs1.files[file] != fs2.files[file]
                content_diff += 1.0
            end
        end
        content_diff /= length(common_files)
    end
    
    return 1.0 - jaccard_sim + 0.5 * content_diff
end

"""
    dependency_distance(d1::DependencyGraph, d2::DependencyGraph) -> Float64

Compute distance between dependency graphs.
"""
function dependency_distance(d1::DependencyGraph, d2::DependencyGraph)
    # Graph edit distance approximation
    nodes_jaccard = if isempty(d1.nodes) && isempty(d2.nodes)
        1.0
    else
        length(d1.nodes ∩ d2.nodes) / length(d1.nodes ∪ d2.nodes)
    end
    
    edges_jaccard = if isempty(d1.edges) && isempty(d2.edges)
        1.0
    else
        length(d1.edges ∩ d2.edges) / length(d1.edges ∪ d2.edges)
    end
    
    return 1.0 - 0.5 * (nodes_jaccard + edges_jaccard)
end

"""
    process_distance(p1::ProcessState, p2::ProcessState) -> Float64

Compute distance between process states.
"""
function process_distance(p1::ProcessState, p2::ProcessState)
    # Simple difference in number of processes and environment variables
    proc_diff = abs(length(p1.running_processes) - length(p2.running_processes))
    env_diff = abs(length(p1.environment_variables) - length(p2.environment_variables))
    
    return min(1.0, (proc_diff + env_diff) / 100.0)
end

"""
    tool_distance(t1::ToolConfiguration, t2::ToolConfiguration) -> Float64

Compute distance between tool configurations.
"""
function tool_distance(t1::ToolConfiguration, t2::ToolConfiguration)
    # Jaccard distance on available tools
    if isempty(t1.available_tools) && isempty(t2.available_tools)
        return 0.0
    end
    
    jaccard_sim = length(t1.available_tools ∩ t2.available_tools) / 
                  length(t1.available_tools ∪ t2.available_tools)
    
    return 1.0 - jaccard_sim
end

"""
    external_distance(e1::ExternalEnvironment, e2::ExternalEnvironment) -> Float64

Compute distance between external environment states.
"""
function external_distance(e1::ExternalEnvironment, e2::ExternalEnvironment)
    # Normalized differences in resource metrics
    load_diff = abs(e1.system_load - e2.system_load) / max(1.0, e1.system_load + e2.system_load)
    
    memory_diff = if e1.available_memory + e2.available_memory > 0
        abs(e1.available_memory - e2.available_memory) / (e1.available_memory + e2.available_memory)
    else
        0.0
    end
    
    disk_diff = if e1.available_disk + e2.available_disk > 0
        abs(e1.available_disk - e2.available_disk) / (e1.available_disk + e2.available_disk)
    else
        0.0
    end
    
    connectivity_diff = e1.network_connectivity != e2.network_connectivity ? 1.0 : 0.0
    
    return 0.25 * (load_diff + memory_diff + disk_diff + connectivity_diff)
end